The present application is the U.S national stage application of International Application PCT/N099/00325, filed Oct. 25, 1999, which international application was published on May 18, 2000 as International Publication WO 00/27218 in the English language. The International Application claims priority of Norwegian Patent Application 19985005, filed Oct. 28, 1998.
The present invention relates to a composite, particulate feed for fry or larvae of other marine organisms. Also, the invention relates to a method of manufacturing this feed.
One of the reasons why the rearing of salmon has become a national and international successful industry today, is, among others things, that this species can easily be fed a Starting feed. The fact that start-feeding and cultivation at the larvae stage are mastered, also appliers to all other species which have had a breakthrough in commercial aqua culture (Watanabe and Kiron 1994). Contrary to salmon, which is start fed with formulated feed, most other relevant reared species are fed live feed as starting feed. This applies to species like the sea bass (Dicentrarchus labrax), gilthead sea bream (Sparus aurata), turbot (Scophtalmus maximus), sole (Solea sp.), cod (Gadus morhua L.) and Atlantic halibut (Hippoglossus hippoglossus) (Person Le Ruyet et al., 1993). Wolffish (Anarhichas lupus) is a marine species which, can easily start fed with formulated feed (Moksness et al. 1989, Strand et al. 1995). A freshwater species like carp (Cyprinus carpio) can also be start-fed with formulated feed. However, in intensive farming it is also recommended for this species to be fed live prey (Kamler 1992) as starting feed. Rotatories and Artemia are the types of live feed which are used the most in intensive rearing systems (Naas et al 1992, Watanabe and Kiron 1994). To obtain the desired nutritional composition, these types are enriched with nutrients before they are offered as feed to the fry/larvae of fish. In semi-intensive systems collected natural animal plankton is used, and an addition of Artemia is used in periods when prey is scarce (van der Meeren and Nxc3xa6ss 1993, Nxc3xa6ss et al. 1995).
Dabrowski (1984) divides larvae of fish into three categories based on the development of the digestive channel. Group 1 is larvae which have a functional stomach at first feed (salmon and wolffish). These species can be start-fed with formulated feed. Group 2 is larvae which develop a stomach later in the ontogenesis (sea bass, gilthead sea bream, Atlantic halibut, turbot, sole and cod). Group 3 is fishes which do not develop a stomach (carp). The problems by feeding formulated feed as the starting feed is connected, first and foremost, to the groups 2 and 3.
A number of tests have been carried out on the ability of fish larvae of enzymatic digestion of feed taken in. (Hjelmeland et al. 1984, Lauff and Hofer 1984, Baragi and Lovell 1986, Pedersen et al 1990, Verreth et al. 1992). The fact that fish larvae which cannot be start-fed with formulated feed, do not have a stomach, has given reason to believe that they may have special requirements as to choice of feed, the digestion in their intestines and their ability to absorb across the intestinal wall. In the extension of this it has also been discussed whether, and to what extent, the fish larvae""s digestion of the feed taken in, is dependent on enzymes in the live feed (Dabrowski and Glokowski 1977 a,b,c, Dabrowska et al 1979, Lauff and Hofer 1984, Lxc3xa9ger et al 1986, Tandler and Kolkovski 1991).
To establish the nutritional requirements of the larvae on start-feeding, it has been suggested that analyses of the composition and consumption of the yolk body (endogen absorption of nourishment) may provide knowledge on this. This approach shows that marine fish eggs, as compared to grown fish, has a high content of nxe2x88x923 fatty acids, phospholipids, free amino acids: and some vitamins and minerals. By means of such analyses, differences between species in the turnover of energy have been disclosed (Rxe2x88x85nnestad et al. 1992, Rxe2x88x85nnestad and al. 1994, Rxe2x88x85nnestad and Fyhn, 1993). Based on the endogen absorption of nourishment larvae may be divided into larvae with a drop of oil in their yolk sacs and larvae without a drop of oil in their yolk sacks. Turbot, sole, sea bass and gilthead sea bream have an oil drop in their yolk sacks whereas cod and Atlantic halibut do not.
Analyses of the chemical composition of natural prey is another approach which has been applied to establish the nutritional requirements of larval fish. The main focus in this context has been on the high level of poly-unsaturated fatty acids, in particular EPA and DHA (20:5 nxe2x88x923 and 22:6 nxe2x88x923) (Sargent et al. 1989, van der Meeren et al. 1993), the high level of phospholipids in nauplii (Sargent et al. 1989) and the content of free aminoacids. (Fyhn 1989).
The nutritional requirements are conventionally studied by performing dose/response experiments, in which the contents of nutrients of the feed are being varied. Because of inadequate feed technology and lack of success, so far, in making the larvae survive on formulated feed, this approach has been possible only through enrichment of the prey. Present feed technology has not been able to provide a feed which allows control of what nutrients the larvae actually do receive. The problems are first and foremost associated with nourishment leaking out from such feed particles.
Internationally a considerable effort has been made to develop a formulated feed for the feeding of larval fish, but a formulated feed which results in just as good survival and growth as live feed from the first feed is yet to be developed (Watanabe and Kiron 1994). Generally, feed for larval fish is prone to water-soluble nutrients leaking out because of the small particle size (large surface relative to volume). The problem connected to the formulation of the starting feed has been to manufacture particles which are both stable in terms of leakage of water-soluble nutrients, and easily digestible to the larva. Without encapsulation (stabilisation of the surface) of the feed, 30-50% of the dry weight are wasted (Urban-Jezierska et al. 1984, Kamler 1992). This loss is represented by xe2x80x9cfine dustxe2x80x9d ( less than 20 xcexcm) and leakage of essential water-soluble components (amino acids, peptides, proteins, vitamins, minerals). A number of methods of micro-encapsulation of starting feed for larval fish has been developed (Teshima et al. 1982). This helps stabilise the particle, but common for all the methods is that the water-soluble components leak out of the feed particle after feeding. An instant loss of up to 80% of leakable material (OD280, i.e. amino acids, peptides, proteins) has been observed in particles between 100-300 xcexcm (Garatun-Tjeldstexe2x88x85 1993). If the particles are made too stable (tight), they will also be indigestible to the larval fish.
Today it is commonly agreed among people of the trade as well as researchers that future rearing of fish on an industrial scale assumes the possibility of being able to use formulated feed as early as possible, preferably from the start. This is because there are several factors of uncertainty attached to the live feed technology. Those are factors associated with the risk of transferring diseases, variable nutritional composition, variable supply of prey through the year, competence connected to the cultivation of prey and costs. The lack of adequately formulated feed, for larvae as a substitute for live feed is a substantial hindrance for the development of a trade of fish farming based on marine species of fish. Accordingly, the trade policy forms the very best basis for increased efforts in the developing and manufacturing of formulated feeds for larval fish.
To control leaks from micro-particulate feed, there has been developed, according to the present invention, a technology based on the use of a cross-linking matrix and phospholipids/biomembranes in the feed. The development of the technology has been based on the considerations that a feed particle for the feeding of larval fish should be given a number of positive qualities, characteristic of an optimal feed organism. It should have:
1. The ability to stay afloat in the water column for a longer time without dissolving.
2. A size, taste and looks that make the want to eat
3. Balanced contents of nutrients.
4. A reduced/controlled leak to the water, so that the nutritional value is not reduced.
5. A controlled leak to the water so that the tastiness of the feed is increased.
6. A high digestibility after intake into the intestine of the fish.
The formulated feed particles developed to solve the problems mentioned above, are characterized, according to the characterizing part of claim 1, by the feed particles consisting of a matrix containing preferably water-insoluble nutrients, the particles having, embedded therein, phospholipids/biomembranes, the biomembranes containing fat-soluble components and packing preferably water-soluble nutrients.
This may be explained in depth in the items 1-11 below:
1. The water-soluble nutritional components of the feed, and any water-soluble additives, are prevented from leaking out by being present encapsulated in phospholipids/biomembranes in the particles.
2. The production of biomembranes in the feed may be carried out according to the European patent document No. 0 158 441 B1.
3. The biomembranes, which are formed of phospholipids, and are a nutrient in themselves, dissolve rapidly in the intestine and release their content.
4. Dependent on their source, the phospholipids may contain marine fatty acids which are essential nutrients for the fish.
5. The particle is produced by the embedding of the phospholipids with water-soluble substances together with other nutrients in a matrix.
6. Water-soluble substances packed in the particle by means of phospholipids to increase the tastiness, are hydrolysed proteins.
7. The size of the particles of wet feed is determined in the manufacturing of the matrix (atomisation).
8. The size of the particles of dry feed are determined in the grinding and sifting.
9. Most of the nutrients of the feed are present as water-insoluble material in the matrix.
10. The technology for cross-linking the feed ensures a low rate of sedimentation of wet feed.
11. The technology for cross-linking the feed and subsequently freeze-drying it, ensures a low rate of sedimentation of the dry feed.
A method of manufacturing this feed for the larvae of fish or other organisms in the sea and in freshwater, excels primarily by the fact that a matrix which contains water-insoluble nutrients, phospholipids/biomembranes containing fat-soluble and water-soluble nutrients, further nutrients and water, is mixed together, is comminuted in a nozzle or similar under the supply of gas and then cross-linking in a suitable solution.